NEW OPTIMIZED LIQUID-LIQUID EXTRACTION METHOD FOR THE REMOVAL  OF THALLIUM AS A MATRIX ELEMENT IN MINERALS

Petre Makreski; Jovica  Todorov; Vasil  Makrievski; Milena  Taseska-Gjorgjijevski; Radojko  Jaćimović; Gligor  Jovanovski; Trajče  Stafilov

Petre Makreski Institute of Chemistry, Faculty of Natural Sciences and Mathematics, Ss Cyril and Methodius University in Skopje, Arhimedova 5, 1000 Skopje, North Macedonia
Jovica Todorov Institute of Chemistry, Faculty of Natural Sciences and Mathematics, Ss Cyril and Methodius University in Skopje, Arhimedova 5, 1000 Skopje, North Macedonia
Vasil Makrievski Institute of Chemistry, Faculty of Natural Sciences and Mathematics, Ss Cyril and Methodius University in Skopje, Arhimedova 5, 1000 Skopje, North Macedonia
Milena Taseska-Gjorgjijevski Institute of Agriculture, Ss. Cyril and Methodius University in Skopje, Blvd. Aleksandar Makedonski b.b., 1000 Skopje, North Macedonia
Radojko Jaćimović Department of Environmental Sciences, Jožef Stefan Institute, Jamova cesta 39, 1000 Ljubljana, Slovenia
Gligor Jovanovski Research Center for Environment and Materials, Macedonian Academy of Sciences and Arts, Blvd. Krste Misirkov 2, 1000 Skopje, North Macedonia
Trajče Stafilov Institute of Chemistry, Faculty of Natural Sciences and Mathematics, Ss Cyril and Methodius University in Skopje, Arhimedova 5, 1000 Skopje, North Macedonia

Keywords: matrix element; lorandite; thallium; trace elements; liquid-liquid extraction; ICP-AES; k0-INAA

Abstract

When screening the content of trace elements in minerals or other inorganic compounds, the detection limit is raised and determination by spectroscopic techniques is often questionable or even impossible due to their interference with the matrix elements of the minerals. Thus, some valuable trace elements may remain undetected, which lowers the estimation for potential economic exploration of the geological deposit or site. Therefore, the main objective of this research was to find a suitable, cost-effective, reliable and rapid method for the selective and consecutive elimination of thallium and arsenic in the analysis of As-Tl minerals and to lower the detection limit for the determination of the trace elements present. The method was based on the separate optimization of the molarity of HCl and the volume of organic solvents including diisopropyl ether, diethyl ether, n-amyl acetate and isoamyl acetate. The optimized HCl concentration enabled the extraction of thallium (as chloride complex) and its migration into the organic top layer. The optimization of the method was performed with
thallium(I) nitrate and then realgar (As4S4) was added to simulate the composition matrix for lorandite (TlAsS2), as the latter mineral is very rare and valuable to be used for screening. In addition, a multi-element standard solution (Ag, Al, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mo, Ni, Pb, Sr, Tl, V, Zn) was used to simulate the trace elements that may be present. Once all conditions were optimized, a two-step liquid-liquid extraction with n-amyl acetate (to eliminate Tl) and toluene with KI (to eliminate As) was performed for the dissolved lorandite. All elements were determined by inductively coupled plasma - atomic emission spectrometry and the results were correlated with those obtained by k0-instrumental neutron activation analysis from the same, previously powdered, lorandite specimen.

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